Recent studies have emphasize the limitations of conventional coronary angiography. Coronary flow reserve has been proposed as a meaningful measure of the physiological significance of lesions. Flow reserve measurement techniques presently under investigation include parametric DSA imaging and quantitative angiography. We propose to investigate the application of parametric DSA flow reserve images which may provide estimates of overall flow reserve as well as information regarding the distribution of flow reserve. Following optimization of the parametric technique, a DSA videodensitometric adaptation of quantitative cineangiography will be tested as a means for estimating flow reserve. Then we will investigate the combined use of parametric and densitometric stenosis measurements to estimate the conductance reserve of the distal vascular bed. Absolute flows, calculated from a combination of videodensitometry and Doppler measurements, will be used for validation. In a multiple lesion animal model the ability of the parametric technique to provide an estimate of overall flow reserve and regional distribution will be studied. Absolute distal bed resistance will be estimated in normal patients and in three single lesion patient subgroups using Doppler validation. We will investigate the hypothesis that resistance ratios determined without Doppler data can be used to identify patients with various combinations of visible stenosis, hypertrophy or collateral flow. Finally, in patients with multiple lesions, overall parametric flow reserve estimates will be compared with Doppler- videodensitometric results.